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THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

PRESENTED  BY 

PROF.  CHARLES  A.  KOFOID  AND 
MRS.  PRUDENCE  W.  KOFOID 


VIII. 

On  Plutygonus  Compressus:  a  new  Fossil  Pachyderm. 
BY  JOHN   L.    LE   CONTE,   M.  D. 


(Communicated  to  the  Academy,  May  29/A,  1848.) 


IN  the  short  notice  of  new  fossil  Mammalia,  published  in  >SV 
marts  Journal  for  January,  1848,  I  have  given  an  account  of  the 
circumstances  under   which   these   bones  were  found,  which  are 
briefly  these. 

At  a  few  miles  distance  from  Galena,  in  Illinois,  while  sinking  a 
shaft  for  the  purpose  of  obtaining  lead  ore,  a  fissure  was  discovered 
fifty  feet  below  the  surface  ;  this  fissure  was  filled  with  an  earthy 
deposit,  containing  much  iron  and  lime,  and  imbedded  in  it  were 
found  many  fragments  of  bone.  A  portion  of  these  were  preserved 
by  the  miners,  and  by  good  fortune  found  their  way  to  the  collec- 
tion of  Mr.  Snyder,  a  merchant  residing  in  Galena,  and  well  known 
for  his  appreciation  of  natural  science.  By  him  some  teeth  were 
presented  to  me  a  few  years  ago,  in  order  to  determine  the  species 
of  animals  to  which  the  bones  belonged.  On  examination,  these 
teeth  were  found  very  different  from  any  heretofore  observed,  and 
it  was  at  once  evident  that  they  appertained  to  one  or  more  new 
genera.  Notice  of  this  fact  was  sent  to  Mr.  Snyder,  and  permis- 
sion was  asked  to  examine  the  other  mammalian  fossils  of  his  cab- 

34 


M363395 


258  ON    PLATYGONUS    COMPRESSUS : 

inet.  Not  only  was  the  request  granted,  but,  with  the  generosity 
of  a  scientific  spirit,  the  entire  collection  was  placed  at  my  dispo- 
sal, that  it  might  be  rendered  more  accessible  to  our  comparative 
anatomists.  Mr.  Snyder  has  also  promised  to  procure  such  other 
specimens  as  may  be  found  in  his  vicinity.  It  is  also  hoped  that 
in  a  short  time  casts  of  the  bones  already  obtained  will  be  ready 
for  distribution  to  the  learned  societies  of  our  country. 

Among  the  specimens  now  in  my  possession  were  detected  re- 
mains of  the  following  animals :  —  Platygonus  compressus  (the  sub- 
ject of  the  present  memoir),  Hyops  depressifrons  (a  new  animal 
allied  to  Dicotyles),  and  a  new  species  of  Procyon.  From  another 
fissure  were  obtained  teeth,  indicating  two  other  new  genera,  which 
are  referred  to  in  the  notice  quoted  above. 

We  new  proceed  to  the  description  of  the  separate  bones  of  the 
first-named  animal,  commencing  with  the  teeth. 

Dentition. 

By  carefully  picking  away  the  cement  which  envelops  the  ante- 
rior part  of  the  fragment  (figs.  1,2),  a  small  external  incisor  was 
discovered  :  the  distance  of  this  tooth  from  the  superior  canine  is 
given  in  the  table  of  measurements  at  the  end  of  the  descriptive 
part  of  this  memoir.  The  bone  is  so  much  mutilated,  that  it  is 
impossible  to  determine  whether  there  were  two  or  three  superior 
incisors  on  each  side  ;  although,  from  the  affinities  of  the  animal, 
there  were  doubtless  three.  In  the  form  of  the  tooth  there  is  noth- 
ing peculiar;  it  has  a  rounded  mammillary  crown,  scarcely  acute 
at  the  summit. 

The  superior  canine  (figs.  9-11)  is  very  much  compressed, 
pointed,  and  curved  ;  the  anterior  edge  almost  sharp  ;  the  posterior 
acute  and  trenchant ;  the  external  face  (fig.  9)  slightly  more  con- 


A   NEW   FOSSIL    PACHYDERM.  259 

vex  than  the  internal,  and  marked  near  the  base  of  the  enamelled 
portion  with  an  acute,  elevated  line,  which  runs  obliquely  to  the 
anterior  edge,  where  it  is  met  bj  a  similar  less  elevated  line  belong- 
ing to  the  internal  face  (fig.  10)  ;  this  latter  line  is  acutely  angu- 
lated  at  the  base,  and  joins  another  elevated  line  which  arises  near 
the  angle  in  the  line  denning  the  enamelled  surface,  and  continues 
parallel  to  the  anterior  margin  about  half-way  to  the  extremity, 
where  it  gradually  vanishes.  The  anterior  margin  is  worn  into  a 
very  narrow  surface,  extending  from  a  to  the  extremity,  b  (fig.  9). 
The  inserted  portion  of  the  tooth  is  slightly  sinuous  on  the  anterior 
margin,  and  is  marked  with  two  very  feeble  grooves  on  the  external 
surface  ;  the  space  between  these  grooves  is  rather  more  convex 
than  the  adjoining  parts.  At  c  (fig.  9),  the  fang  is  slightly  con- 
tracted. 

The  only  teeth  I  have  seen  figured,  which  can  be  compared 
with  the  present  specimen,  are  the  canines  of  the  genus  Machai- 
rodus,  which  are,  however,  distinguished  by  the  curiously  serrate 
edges,  and  the  absence  of  the  oblique  basal  lines  so  characteristic 
of  Platygonus. 

The  superior  premolars  are  shown  in  figs.  12  and  13  (p.  3,  p.  4). 
That  p.  4  (fig.  13)  must  be  considered  a  premolar  is  evident  from 
an  inspection  of  fig.  2,  in  which  are  seen  three  premolars  in  place, 
while  the  socket  of  the  fourth  is  quite  distinct.  In  my  notice  of 
this  genus  in  Silliman's  Journal  (loc.  cit.  p.  103),  it  is  stated  that 
there  are  but  three  premolars ;  I  had  not  then  cleaned  away  the 
cement  in  which  the  socket  (p.  4,  fig.  2)  was  concealed ;  I  also 
considered  m.  1  (fig.  13)  as  the  penultimate  molar,  but  on  compar- 
ing it  with  the  tooth  anterior  to  fig.  13',  it  shows  minute  differences, 
which  will  be  detailed  below. 

The  first  premolar,  right  side,  p.  1  (fig.   12),  is  triangular,  with 


260  ON    PLATYGONUS    COMPRESSUS : 

rounded  angles  ;  the  crown  rises  externally  into  a  subquadrangular 
tubercle,  which  is  impressed  anteriorly  and  posteriorly ;  the  external 
surface  of  this  elevation  is  continuous  with  the  margin  of  the  tooth, 
while  on  the  other  sides  it  is  surrounded  by  a  broad  cingulum,  which 
is  wider  posteriorly.  In  the  younger  individual  (fig.  2),  this  cingu- 
lum rises  into  an  acute  ridge,  which  is  foveate  on  the  anterior  and 
interior  portions. 

The  second  premolar,  p.  2  (figs.  2  and  12),  is  subtriangular,  slightly 
transverse,  with  a  large  transverse  elevation,  and  an  anterior  and 
posterior  basal  margin,  which  nearly  unite  on  the  external  face  in 
the  younger  specimen.  The  transverse  elevation  is  divided  into  two 
cusps,  by  a  deep  antero-posterior  incision,  and  the  posterior  basal 
margin,  at  the  external  angle,  rises  into  a  small  tubercle. 

The  third  premolar,  left  side,  p.  3  (figs  2  and  13),  is  subquadrate, 
transverse,  and  a  little  narrowed  internally ;  it  is  furnished  with 
transverse  elevation  and  basal  margins,  as  in  the  preceding,  but  they 
are  more  strongly  marked :  the  external  pyramid  is  slightly  pro- 
duced anteriorly,  and  descends  almost  to  the  margin  of  the  tooth. 

The  fourth  premolar,  left  side,  p.  4  (fig.  13),  is  similar  to  the  molar 
next  described  in  all  its  sculpture,  but  is  smaller,  and  the  shape 
slightly  different ;  the  internal  margin  is  scarcely  emarginate,  and 
the  anterior  margin  is  not  oblique,  but  very  slightly  sinuous,  for  the 
curve  of  the  3d  premolar. 

The  first  molar,  m.  I  (fig.  13),  is  quadrate,  with  two  large  trans- 
verse elevations,  each  of  which  is  divided  into  two  pyramids,  or 
cusps,  the  external  being  smaller ;  the  internal  posterior  pyramid  is 
produced  obliquely  outwards  to  the  posterior  margin  ;  the  internal 
anterior  pyramid  sends  a  similar  but  smaller  prolongation  to  the 
anterior  margin.  The  basal  cingulum  is  well  developed  on  the 
anterior,  external,  and  posterior  margins,  except  where  it  is  sub- 


A  NEW   FOSSIL    PACHYDERM.  261 

interrupted  bj  the  prolongation  of  the  posterior  internal  pyramid. 
There  is  no  internal  basal  margin,  except  at  the  expansion  of  the 
valley  between  the  ridges.  This  valley  is  deeper  at  the  extrem- 
ities than  in  the  middle,  where  it  is  penetrated  by  an  anterior  pro- 
longation of  the  posterior  internal  pyramid.  The  anterior  margin 
of  this  tooth  is  oblique,  the  external  angle  being  prominent,  and 
more  rounded  than  the  internal.  This  proves  the  existence  of  a 
slight  angle  at  the  junction  of  the  molar  with  the  premolar  series, 
to  accommodate  the  position  of  the  teeth  to  the  compressed  form  of 
the  head  anterior  to  the  molars.  The  line  of  insertion  of  the  in- 
ferior molars  follows  the  same  course,  and  will  be  found  hereafter 
to  strengthen  this  deduction. 

The  second  molar  is  quite  similar  to  the  first,  but  is  regularly 
quadrate,  the  anterior  margin  not  being  oblique  ;  the  figure  and  de- 
scription already  given  will  serve  to  identify  it  perfectly.  It  may 
be  stated  that  this  tooth  was  found  in  juxtaposition  with  the  third 
molar ;  the  whole  series  of  that  side  were  imbedded  in  a  thin  mass 
of  very  hard  cement,  but  the  roots  having  entirely  decayed,  the 
specimens  were  so  fragile,  that,  in  endeavouring  to  expose  the 
crowns,  the  first  molar  was  entirely  destroyed  ;  for  this  reason,  the 
third  and  fourth  premolars,  and  first  molar,  are  figured  from  an  older 
and  slightly  larger  specimen  than  the  one  which  furnished  the  third 
molar. 

The  third  molar,  m.  3  (fig.  13'),  also  of  the  left  side,  is  longer  than 
wide,  slightly  narrowed  behind,  emarginate  on  the  sides,  with  the  an- 
terior external  angle  a  little  prominent,  and  more  suddenly  rounded ; 
the  sculpture  is  similar  to  that  of  the  first  and  second  molars,  but 
in  addition,  the  posterior  basal  cingulum  rises  into  a  small  uneven 
cusp,  connected  with  the  internal  pyramid  of  the  posterior  em- 
inence :  on  the  externo-posterior  face  of  this  pyramid  a  trapezoidal 
plane  is  developed  by  wearing,  extending  to  the  basal  cusp. 


262  ON  PLATYGONUS  COMPRESSUS : 

All  these  teeth,  by  wearing,  lose  the  separation  between  the 
cusps  of  the  transverse  elevations,  which  thus  become  broad  and 
straight  ridges,  having  the  extremities  a  little  more  elevated  than 
the  middle. 

In  the  fragment  of  the  lower  maxilla,  only  the  second  and  third 
molars  are  preserved.  There  are  remains  of  the  fast  molar  and  the 
posterior  premolar,  but  not  sufficient  for  description. 

The  second  molar,  m.  2  (fig.  7),  is  quadrangular,  with  rounded 
extremities  and  somewhat  emarginate  sides ;  it  presents  two  large 
transverse  ridges  separated  by  a  deep  valley ;  there  is  a  very  slight 
anterior  and  posterior  basal  margin,  more  elevated  in  the  middle ;  the 
valley  has  a  very  indistinct  margin  externally,  and  at  that  place  the 
anterior  lobe  rises  suddenly,  so  as  to  form  a  very  well  defined  right 
angle  with  the  margin  ;  there  is  another  angle,  but  less  sharply 
defined,  between  the  same  margin  and  the  posterior  lobe. 

The  third  molar,  m.  3  (fig.  7),  is  elongated,  narrowed  and  round- 
ed posteriorly,  scarcely  emarginate  on  the  sides ;  it  has  two  large 
transverse  lobes,  as  in  the  preceding,  a  very  obsolete  anterior  basal 
margin,  and  a  large  posterior  undivided  lobe,  acute  at  the  top,  and 
almost  as  much  elevated  as  the  two  principal  lobes.  This  lobe  is 
separated  from  the  second  lobe  by  a  valley,  acute  at  the  bottom, 
and  a  little  deeper  internally  than  externally ;  into  which  fits  the 
small  posterior  cusp  of  the  third  superior  molar.  The  valley  sep- 
arating the  second  from  the  first  lobe  is  wide,  and  deeper  inter- 
nally. At  the  outer  part  it  has  a  small  horizontal  triangular  face  (a) ; 
and  the  external  margin  of  this  face  forms  with  the  anterior  lobe 
a  very  distinct  obtuse  angle  :  with  the  second  lobe  it  forms  a  less 
distinct  right  angle.  It  is  to  be  observed  that  the  internal  extrem- 
ities of  the  transverse  lobes  of  these  lower  molars  are  more  elevated 
than  the  external  parts. 


A   NEW   FOSSIL   PACHYDERM. 


263 


These  two  molars  are  inserted  in  a  line  slightly  oblique  outwards 
with  reference  to  the  long  axis  of  the  bone  ;  the  first  molar  contin- 
ues this  line,  but  the  roots  of  the  premolar,  as  well  as  a  slight  flex- 
ure in  the  bone,  indicate  that  the  line  of  insertion  there  changes 
its  direction  by  bending  inwards,  to  a  degree  which  would  probably 
make  it  parallel  with  the  line  of  the  opposite  side.  This  agrees 
with  the  inference  from  the  form  of  the  first  superior  molar,  and  also 
with  the  shape  of  the  cranium  hereafter  described.  The  dentition 
as  far  as  determined  is,  — 

inc.  ^T—-  can.  — ;  prem.  — ;  mol.  !n?; 

r  1^—1  •*•  t        '  3 —  3 

which  agrees  with  the  general  formula  for  the  Tapiroidea;  to  which 
group  of  Pachyderms  the  teeth,  from  their  separate  characters, 
would  most  naturally  be  referred. 

The  measurements  of  the  teeth  described,  in  English  inches,  are 
as  follows :  — 


Length.  Breadth. 

1st  superior  premolar,  .35  .32 

2d        "  "  .41  .47 

3d        "  "  .43  .50 

4th  id.  (from  larger  spec.),  .50  .46 

1st  molar  (larger  spec.),  .65  -55 

2d  molar,  .61  .55 

3d  molar,  .77 


Length.  Breadth. 

1st  inferior  molar,                  .46  ? 

2d         "         "                       ,60  47 

3d        "        "                       .78  .45 

Dimensions  of  superior  canine. 

Length  of  exserted  part,  1.59 
Breadth  of  lateral  surfaces  at  base 

of  exserted  portion,  .50 


(Breadth  anteriorly,  62  ;  post.,  .56.)         Thickness  of  tooth, 


.30 


Bones  of  the  Head, 

The  portions  of  the  skull  obtained  are,  —  the  anterior  part  of  the 
upper  jaw ;  the  posterior  part  of  the  os  frontis ;  part  of  one  os  mala- 
rum,  with  the  os  lachrymale  ;  portions  of  the  palatal  plate  of  su- 
perior maxilla ;  and  the  posterior  part  of  the  inferior  maxilla. 

The  first-mentioned  fragment  is  represented,  fig.  1,  side  view ; 


264  ON    PLATYGONUS    COMPRESSUS : 

fig.  2,  base  view  ;  fig.  5,  A,  top  view.  From  it  we  learn  that  the 
head  was  very  narrow,  and  compressed  on  the  sides  ;  the  canines 
were  concealed  by  the  lips,  and  projected  forwards  downwards,  and 
a  little  outwards.  The  malar  plate  of  the  superior  maxilla  is  ex- 
panded very  obliquely  outwards,  and  above  it  is  a  wide  but  shallow 
groove  (a,  a,  fig.  1),  which  is  parallel  with  the  superior  suture,  and 
vanishes  opposite  the  first  premolar. 

Above  the  superior  canine,  the  bone  swells  out  into  a  somewhat 
acute  prominence,  from  which  a  concavity  (f,  A,  fig.  5),  expand- 
ing as  it  advances,  looking  outwards  and  a  little  forwards,  runs 
towards  the  incisor.  The  suture  of  the  intermaxillary  bone  passes 
upwards  and  backwards  very  close  to  the  canine,  and  almost  in 
contact  with  the  anterior  wall  of  its  socket. 

The  ossa  nasi  are  very  convex  from  side  to  side,  forming  a  semi- 
circular arch  ;  they  are  also  very  slightly  arched  antero-posteriorly. 
About  the  region  of  the  canines,  the  skull  expands  a  little,  the  lat- 
eral surfaces  being  there  flattened  and  oblique.  From  a  small  frag- 
ment (fig.  3),  containing  the  root  of  the  first  premolar,  it  will  be 
seen  that  an  elevated  line  originates  opposite  that  tooth,  and  is  lost 
before  reaching  the  canine  ;  this  line  is  parallel  to  the  alveolar  mar- 
gin; immediately  above  it,  and  a  little  anterior  to  the  first  premolar, 
is  a  small  foramen  (a,  fig.  3).  Below  the  elevated  line  is  a  deep 
longitudinal  concavity,  oblique  downwards,  separated  from  the  pala- 
tal plate  by  a  second  elevated  line.  The  palatal  plate  is  seen  in 
fig.  2 ;  it  is  concave  transversely,  with  flattened  sides ;  by  pick- 
ing away  the  cement  at  the  anterior  part  of  the  fragment,  it  ap- 
peared that  this  concavity  becomes  more  narrow  anteriorly,  at  the 
same  time  increasing  in  depth,  until  it  assumes  the  form  of  a  medial 
groove.  On  each  side  are  the  remains  of  a  deep  groove  (a,  a, 
fig.  2)  ;  and  by  reference  to  the  palatal  part  of  the  small  fragment 


A   NEW   FOSSIL    PACHYDERM.  265 

just  mentioned,  this  groove  is  seen  to  be  double,  the  external  groove 
being  in  contact  with  the  alveolar  margin ;  the  interior  of  these 
grooves  is  deeper,  and  perforates  the  plate  immediately  opposite  the 
first  premolar.  Another  fragment  containing  molars  shows  a  flat- 
tened surface,  rough  with  longitudinal  grooves  and  elevations 
towards  the  side,  as  if  worm-eaten. 

The  os  frontis  is  seen  in  fig.  4.  The'jposterior  contour  is  round- 
ed almost  in  the  arc  of  a  circle  ;  the  posterior  edge  is  bevelled  off 
very  obliquely,  and  striate  for  the  adaptation  of  the  ossa  parietalia, 
which  have  not  been  obtained.  The  approximation  of  the  post- 
orbital  processes  is  remarkable ;  they  project  laterally,  having 
scarcely  any  tendency  downwards ;  the  superior  surface  of  the 
bone  is  much  flattened,  being  scarcely  more  elevated  in  the  middle 
than  at  the  sides. 

Fig.  5  represents  the  parts  already  described,  in  their  relative 
position,  with  the  addition  of  (5)  the  malar  bone  and  part  of  the 
lachrymal.  The  external  surface  of  these  bones  is  flat,  and  looks 
forwards  and  outwards,  but  not  at  all  upwards ;  the  posterior  orbi- 
tal process  (a)  is  very  long,  acute,  and  bent  inwards  at  the  point  ; 
at  d  is  an  indication  of  a  wide,  shallow  groove  ;  b  is  the  lachry- 
mal tubercle,  more  elevated  than  in  Dicotyles,  and  placed  on  the 
margin  of  the  orbit ;  anterior  to  this  the  surface  looks  directly  up- 
wards ;  at  the  base  of  the  lachrymal  tubercle  is  (c)  a  groove,  in 
which  are  placed  the  lachrymal ;  anterior  to  this  is  (e)  a  slight  con- 
cavity. In  the  position  of  the  groove  and  foramina  with  reference 
to  the  tubercle,  a  striking  difference  will  be  observed  between  this 
animal  and  its  allies ;  the  orbital  plate  is  behind  the  tubercle,  and 
looks  inwards  and  backwards,  the  groove  and  foramina  being  alto- 
gether external.  In  Dicotyles,  the  orbital  plate  looks  directly  back- 
wards, and  the  foramina  are  situated  internally.  In  Tapirus  (ac- 

35 


266  ON    PLATYGONUS    COMPRESSUS : 

cording  to  Cuvier),  the  same  foramina  are  on  the  edge  of  the  orbit. 
The  fragment  of  malar  and  lachrymal  bones  is  represented  in  a 
side  view  (fig.  6),  to  show  the  flatness  of  the  external  surface,  and 
also  a  small  foramen  ;  the  other  parts  are  lettered  as  above. 

Fig.  7  is  the  lower  jaw.  It  is  very  deep  ;  the  articular  surface 
is  placed  obliquely,  and  formed  as  in  Sus  and  Dicotyles ;  but  the 
anterior  margin  is  less  prominent  from  the  neck  of  the  condyle  at 
its  external  part ;  there  is  also  a  small  external  fossa  (a,  fig.  7), 
which  does  not  appear  in  the  animals  just  mentioned.  The  line 
from  the  condyle  to  the  posterior  molar  is  three  fourths  of  an  inch 
longer  than  in  Dicotyles  torquatus,  and  passes  more  obliquely  in- 
wards ;  which  corresponds  with  the  great  posterior  expansion  men- 
tioned in  describing  the  cranium.  Below  the  molars  the  bone  swells 
out  slightly,  but  not  so  much  as  in  Dicotyles  ;  the  inferior  margin  is 
rounded,  and  but  little  attenuated  :  it  is  deeply  concave  in  a  longi- 
tudinal direction  ;  this  form  is  caused  by  the  expansion  of  the  angle 
of  the  jaw.  The  expansion  commences  at  a  point  immediately 
below  the  anterior  lobe  of  the  posterior  molar ;  it  does  not  extend 
backwards  to  form  a  process  or  hook,  as  in  Carnivora  and  Roden- 
tia;  nor  does  it  interrupt  the  slight  but  regular  concavity  of  the 
posterior  margin,  which  is  thin,  and  destitute  of  any  prominent 
lines.  The  expanded  part  is  very  concave  on  the  outer  surface  ; 
the  inferior  margin  is  rounded,  as  in  the  figure,  and  projects  far 
outwards,  especially  anteriorly.*  Towards  the  fractured  end  the 
bone  is  expanded,  and  has  a  large  cavity  for  the  reception  of  a  ca- 
nine (fig.  8)  ;  but  as  this  cavity  is  filled  with  the  same  hard  cement 
which  envelops  many  of  the  specimens,  it  is  impossible  to  judge  of 


*  The  perspective  of  this  part  of  the  figure  is  not  good  ;  the  anterior  part  of  the 
expansion  (towards  the  dotted  line)  should  be  in  higher  relief. 


A   NEW   FOSSIL    PACHYDERM.  267 

the  form  of  the  root  of  the  canine.     The  internal  surface  of  the 
bone  is  also  concealed  by  cement. 

Bones  of  the  Trunk. 

A  dorsal  vertebra  is  represented  in  figs.  14-16.  The  body  is 
very  much  compressed  inferiorly,  with  a  sharp  prominent  middle 
ridge  ;  the  anterior  surface  is  concave,  the  posterior  convex ;  the 
peculiarities  of  the  bone  are  better  expressed  in  the  figure  than 
they  can  be  by  any  description. 

A  lumbar  vertebra  (figs.  17,  18)  has  the  body  still  more  concave 
on  the  sides,  and  still  more  compressed  inferiorly,  the  elevated  line 
rising  quite  suddenly,  and  being  very  prominent  (p),  the  posterior 
face  is  concave,  and  looks  a  little  upwards  ;  on  the  side  of  the 
body,  at  the  posterior  part,  is  (a)  an  obtusely  elevated  line,  running 
obliquely  upwards  ;  anterior  to  this  is  a  small  tubercle  (6)  ;  about 
the  middle,  and  at  the  base  of  the  medial  ridge,  is  (c)  a  small  fora- 
men ;  and  a  small  but  deep  fossa  (d)  is  found  close  to  the  base  of 
the  transverse  process. 

Os  innominatum  has  the  ilium  inferiorly  narrow  and  compressed  ; 
above  the  acetabulum,  but  near  its  margin,  are  two  fossae,  which 
extend  upwards  and  shortly  vanish  ;  the  posterior  of  these  is  nar- 
rowed about  its  middle  by  an  elevation  proceeding  from  its  posterior 
lip.  The  external  surface  of  the  ischium  below  the  acetabulum 
is  free  from  elevations,  and  seems  to  be  scarcely  concave  ;  the  pos- 
terior edge  is  thin  and  compressed.  The  bone  is  so  imperfect,  that 
a  figute  would  be  of  little  value. 

Bones  of  the  Extremities. 

The  humerus  (figs.  19,  20,  bone  of  the  right  side),  of  which  the 
lower  part  is  preserved,  is  pierced  by  a  large  foramen.  The  lower 


268  ON    PLATYGONUS    COMPRESSUS : 

head  is  oblique  inwards  ;  the  articular  surface  is  regularly  concave 
behind;  anteriorly  it  has  two  pulley-shaped  grooves,  the  interior 
being  broader,  but  not  shallower,  than  the  exterior  ;  the  interven- 
ing ridge  is  obtusely  rounded,  broad,  and  as  much  elevated  as  the 
sides ;  a  transverse  depression  separates  the  articular  surface  from 
the  edge  of  the  foramen  ;  the  internal  condyle  is  fractured,  the  ex- 
ternal is  flatly  truncate  anteriorly,  with  a  groove  continuous  with 
the  transverse  depression  just  mentioned ;  this  groove  runs  down- 
wards, and  vanishes  towards  the  lower  edge  of  the  condyle.  Pos- 
teriorly, as  shown  by  another  much  mutilated  specimen,  this  condyle 
is  marked  with  two  small  grooves,  which  run  in  the  direction  of  the 
interior  or  narrow  pulley-shaped  surface;  but  this  part  being  covered 
by  cement,  I  know  not  whether  they  meet  the  articular  surface. 
Other  peculiarities  will  be  better  seen  in  the  figure  than  expressed 
in  description.  Immediately  above  the  groove,  on  the  outer  truncate 
surface  of  the  condyle,  the  bone  is  dilated,  and  then  regularly  con- 
tracted to  the  shaft.  The  cavity  for  the  olecranon  is  very  deep. 

The  bone  of  the  cubitus  (fig.  21,  left  side)  is  comparatively  thick, 
and  much  bent,  the  concavity  of  the  curve  looking  backwards. 
The  radius  and  ulna  are  so  fused  together  as  to  be  scarcely  distin- 
guishable. The  shaft  is  subtriangular,  the  external  edge  being 
acute  and  much  compressed  ;  the  anterior  and  internal  edges  are 
indistinct.  The  anterior  face  is  broadly  concave,  adjacent  to  the 
compressed  edge.  The  superior  head  of  the  bone  is  furnished  with 
articular  surfaces  corresponding  to  those  of  the  humerus ;  they  are 
separated  by  two  elevations  extending  from  before  backwards. 
The  internal  surface  looks  inwards  and  upwards,  and  is  equal  to 
the  middle  one  ;  the  external  surface  looks  outwards  and  upwards  ; 
behind  the  middle  surface,  at  the  base  of  the  olecranon,  is  a  deep 
concavity,  separated  at  the  bottom  into  three  unequal  parts :  dividing 


A    NEW   FOSSIL    PACHYDERM.  269 

the  internal  concave  surface,  at  the  base  of  the  olecranon,  is  a  nar- 
row groove,  with  a  depression  behind  the  interior  ridge.  The  low- 
er extremity  is  dilated,  so  that  the  internal  edge  of  the  shaft  is 
rendered  concave  ;  anteriorly  this  extremity  is  convex,  posteriorly 
flat  ;  the  styloid  process  (a)  is  short,  and  immediately  above  it  is  a 
slight  concavity.  The  lower  articular  surfaces  are  shown  in  fig. 
22,  a  being  the  styloid  process.  The  other  faces  for  the  scaphoid, 
semilunar  and  cuneiform,  are  so  well  defined  as  scarcely  to  need 
description  ;  and  the  more  so,  because,  from  the  meagreness  of  our 
museums,  I  have  not  been  able  to  make  comparison  with  the  cor- 
responding parts  of  other  Ungulata.  There  is  very  little  resem- 
blance between  the  present  specimen  and  the'  antebrachium  of  a 
hog ;  the  resemblance  to  a  horse  is  much  more  decided,  but  the 
lower  articular  surfaces  are  quite  different  in  form. 

Os  calcis.  —  The  bone  of  the  left  side  was  found  with  both  ex- 
tremities fractured  ;  the  shaft  flattened,  with  rounded  edges  :  the 
inferior  margin  (concave  in  Sus~)  is  perfectly  straight ;  the  superior 
is  scarcely  concave  ;  the  large  process  for  articulation,  with  the 
astragalus,  is  much  thickened  inferiorly,  and  marked  with  a  slight 
groove.  The  articular  surface  is  scarcely  longer  than  wide,  slightly- 
concave  ;  superiorly  it  is  scarcely  prominent  beyond  the  margin  of 
the  shaft :  the  hollow  below  this  process  is  regularly  narrowed,  but 
there  is  no  fossa  superiorly  between  the  articular  face  and  the  an- 
terior part  of  the  bone.  In  the  common  hog  there  is  a  very  distinct 
fossa. 

Os  cuboides.  —  The  bone  of  the  left  side  is  shown  in  fig.  25,  ex- 
ternal view ;  and  fig.  26,  internal  view.  The  surface  for  the  calca- 
neum  is  long  and  sinuous,  as  in  Sus,  but  the  depression  (a)  is  much 
deeper ;  between  this  surface  and  that  for  the  astragalus  is  (b) 
a  deep  groove,  rounded  at  the  extremity,  extending  almost  to  the 
concavity  (a).  The  astragalian  surface  is  deeply  concave,  and 


270  ON    PLATYGONUS    COMPRESSUS : 

looks  backwards,  but  not  at  all  inwards ;  its  length  is  five  times 
greater  than  its  breadth.  Anteriorly  the  groove  (c)  is  very  deep  ; 
the  face  for  the  metatarsal  (d)  is  subtriangular,  with  rounded  an- 
gles, the  internal  angle  being  more  produced  ;  the  inner  side  of 
this  articular  face  is  slightly  emarginate,  but  there  is  no  fovea  under 
the  emargination,  as  in  Sus :  the  prominence  (h)  is  furnished  with 
a  narrow,  oblique,  articular  face,  for  a  rudimentary  external  meta- 
tarsal. Internally  is  (e)  an  oblong  tubercle,  with  an  acute  edge  ; 
the  posterior  face  of  this  tubercle  is  articular  for  the  scaphoides  ; 
at  the  inferior  part  of  this  surface  is  (/)  a  long  irregular  articular 
surface,  also  for  the  scaphoides  ;  it  is  emarginate  superiorly,  with  a 
depression  at  g.  The  superior  surface  of  the  bone,  owing  to  the 
extension  of  the  calcaneal  face  in  an  anterior  direction,  is  shaped 
somewhat  like  the  small  Greek  n,  and  has  an  elevated  line  parallel 
to  the  anterior  margin. 

The  medial  metatarsal  of  the  right  side  (figs.  23,  24)  has  a  tri- 
angular shaft,  the  external  and  posterior  faces  flattened,  and  meet- 
ing almost  perpendicularly,  the  other  face  being  rounded  almost  in 
a  quadrant ;  the  line  between  the  posterior  and  internal  or  curved 
face  is  strongly  marked  above,  but  fades  out  at  g  (fig.  23)  ;  the 
line  between  the  posterior  and  internal  (a,  a)  is  more  strong  below, 
but  becomes  obsolete  above,  where  it  tends  towards  the  anterior 
process  (e,  e)  ;  the  anterior  edge  (/)  is  well  marked  for  the  whole 
length  of  the  bone.  The  upper  extremity  is  articular  for  the  large 
cuneiform,  with  a  small  surface  at  the  internal  angle  for  the  second 
cuneiform  ;  the  line  in  which  these  unite  is  very  indistinct,  and 
commences  at  the  cusp  (d).  The  large  articular  face  is  concave 
towards  the  antero-internal  part,  and  there  extends  much  lower  on 
the  bone  (vid.  fig.  24).  The  anterior  angle  of  the  upper  extremity 
of  the  bone  is  produced  into  a  curved  truncate  process,  furnished 
with  two  articular  facets  (e,  e').  The  posterior  internal  angle  is 


A   NEW   FOSSIL    PACHYDERM. 


271 


also  furnished  with  a  small  lateral  articular  face  (6).  On  the  pos- 
terior face  of  the  bone,  near  the  extremity,  arc  two  deep  fossae 
(c,  c',  fig.  23),  provided  with  articular  facets  for  the  internal  meta- 
tarsal,  which  is  thus  shown  to  have  been  posterior,  but  by  no 
means  rudimentary.  The  lower  apophysis  is  unfortunately  want- 
ing ;  but  what  remains  is  much  longer  and  more  slender  than 
the  corresponding  part  of  Sus  Scrofa,  and  shows  plainly  that  the 
comparatively  slender  form  of  the  head  and  humerus  was  continued 
even  to  the  feet. 

Measurements  of  the  Fragments. 

CRANIUM.  INFERIOR  MAXILLA. 

Inches.  Inches. 

Incisor  to  centre  of  canine  (figs.  1  Exterior  margin  of  condyle  to  pos- 

1.20 


and  2),       .... 

Incisor  to  anterior  edge  of  1st  pre- 
molar,  .... 

Incisor  to  posterior  edge  of  3d  pre- 
molar,  .... 

Centre  of  canine  to  anterior  edge 

D 

of  1st  premolar,  .         .         2.10 

Distance  between  broken  extrem- 


terior  angle  of  3d  molar,      .         2.80 
Do.  to  anterior  edge  of  2d  molar,      4.00 
3.43    Depth  of  jaw  at  posterior  lobe  of 


4.40 


1st  molar, 

Do.  at  anterior  lobe  of  3d  molar, 
Depth  of  curve  of  inferior  margin 
(measured    from    a    horizontal 
line),  .... 


ities  of  canines, 

Height  from  palatal  plate,  opposite 
1st  premolar,  to  top  of  nasal 
arch, 

Transverse  diameter  at  same  point,    1.35 

Transverse  distance  between  inter- 
nal margins  of  2d  premolar  (cal- 
culated), .... 

Transverse  distance  between  post- 
orbital  processes  of  os  frontis, 

From  last  line  to  middle  of  poste- 
rior curve  of  external  surface 
(being  the  versed  sine  of  the 
curve),  .... 


2.05    Depth  of  concavity  of  external  sur- 
face, 


2.43 


2.20 
3.00 


1.35 


.30 


EXTREMITIES. 

All  the  figures  are  made  of  the  natural 
size,  so  that  only  the  following  measure- 
ments are  necessary :  — 
1.00    Length  of  metatarsal  (fig.  23), 


2.40 


Breadth  of  surface  (a,  /)  superi- 


3.20 


orly, 30 

Do.  inferiorly,  .  .  .  .60 
Anterior  edge  of  e  to  posterior 

of  b, 55 

97  Point  of  process  (e,  e')  to  cusp  (d),  .60 


272  ON    PLATYGONUS    COMPRESSUS : 

Conclusions. 

From  the  foregoing  account,  it  will  be  seen  that  our  animal  pre- 
sents an  assemblage  of  characters  not  found  in  any  other  genus, 
fossil  or  recent.  From  the  form  of  the  teeth,  and  the  concealment 
of  the  canines,  it  evidently  tends  towards  the  Tapiroids,  and  more 
especially  towards  Sophiodon,  and  it  should  be  numbered  among 
the  aberrant  forms  of  that  group.;  nevertheless,  it  differs  from  both 
Tapirus  and  Sophiodon,  in  the  very  compressed  and  trenchant  form 
of  the  canines.  The  extreme  narrowness  of  the  worn  face  of  the 
superior  canine,  together  with  the  oblique  position  of  the  tooth, 
indicates  a  decussation  with  another  narrow  and  pointed  tooth  of 
the  inferior  maxilla.  This  structure  is  well  adapted  for  piercing 
and  cutting  soft  substances,  and  manifests  a  strongly  carnivorous 
habit.  This  inference  is  not  borne  out  by  the  form  of  the  pre- 
molars,  but  it  must  be  remembered  that  the  cutting  form  of  those 
teeth  is  always  more  developed  in  the  lower  jaw  ;  the  structure  of 
the  upper  premolars  in  Dicotyles  is  very  similar  to  that  existing  in 
the  present  genus.  The  absence,  however,  of  accessary  tubercles 
in  the  molars  shows  the  suiline  affinities  indicated  by  some  other 
bones  to  have  been  quite  feeble. 

The  fragments  of  the  cranium  lead  us  to  infer  that  that  portion 
was  very  much  compressed  laterally,  with  an  anterior  and  posterior 
expansion,  the  latter  being  much  greater.  The  arch  of  the  nasal 
bones  being  complete,  and  extending  far  forwards,  it  is  obvious  that 
the  movable  snout  (if  any)  was  extremely  short.  The  malar  bones 
descended  almost  perpendicularly,  looking  forwards  and  outwards, 
while  the  remains  of  the  orbit  of  the  eye  show  that  organ  to  have 
directed  outwards  and  a  little  upwards.  The  flatness  of  the  os 
frontis  and  the  approximation  of  the  eyes  continue  to  the  upper 


A   NEW   FOSSIL   PACHYDERM.  273 

and  posterior  parts  of  the  cranium  the  peculiar  narrowness  which 
gives  to  the  anterior  portion  such  an  extraordinary  appearance. 
The  singular  position  of  the  lachrymal  foramina,  external  to  the 
orbit,  and  anterior  to  the  lachrymal  tubercle,  as  well  as  the  upward 
aspect  of  that  part  of  the  bone  (almost  perpendicular  to  the  exter- 
nal face),  will  also  be  found  worthy  of  remark. 

In  the  lower  jaw  we  observe  farther  evidence  of  this  great  com- 
pression, while  the  inferior  expansion  of  the  bone  around  the  angle 
is  observed  only  in  the  hippopotamus  among  existing  pachyder- 
mata,  and  in  that  genus  on  a  much  less  extensive  scale.  As  the 
posterior  margin  of  the  maxilla  is  somewhat  concave,  this  expan- 
sion must  be  considered  as  a  much  modified  development  of  the 
ferine  type,  in  which  the  expansion  is  continued  directly  back- 
wards. 

From  an  attentive  study  of  the  os  cuboides  and  metatarsal,  k 
will  be  seen  that  Platygonus  combines  the  characters  of  the  Iso- 
dactyle  with  those  of  the  Anisodactyle  Ungulata,  retaining  at  the 
same  time  the  essential  characters  of  the  latter.  It  appears  to  have 
had  three  well-developed  toes,  with  a  rudimentary  external  toe; 
the  relation  existing  between  the  astragalian  and  calcaneal  faces 
of  the  cuboides  is  different  from  any  that  I  can  find  described. 
But  being  obliged  to  deduce  these  analogies  from  drawings  and 
descriptions,  without  reference  to  specimens,  the  observations  must 
necessarily  be  imperfect,  and  I  am  therefore  unable  to  draw  the 
inferences  which  would  become  obvious  to  a  student  having  access 
to  the  great  museums  of  Europe. 

The  study  of  the  bone  of  the  antebrachium  is  more  satisfactory : 
the  radius  and  ulna  are  firmly  anchylosed  throughout  their  whole 
length,  and  the  inferior  surfaces  resemble  closely  those  of  rumi- 
nants, without  being  identical  ;  the  two  elevated  lines  separating 
36 


274  ON    PLATYGONUS    COMPRESSUS. 

the  articular  faces  for  the  scaphoides,  semilunare,  and  cuneiforme 
are  very  oblique,  as  in  the  group  just  mentioned.  The  double 
groove  of  the  lower  articular  surface  of  the  humerus  also  shows  an 
approach  towards  the  ruminant  and  suiline  tribes,  while  the  large 
foramen  of  the  coronoid  cavity  is  a  character  found  in  but  few  spe- 
cies, and,  with  the  very  oblique  external  contour,  serves  very  well 
to  distinguish  the  bone  of  the  present  genus,  when  the  articular 
part  is  destroyed.  The  obliquity  of  the  inferior  head,  with  refer- 
ence to  the  long  axis  of  the  bone,  is  much  greater  than  in  Sus  ;  and 
the  external  pulley  very  much  deeper  than  in  Sus  or  any  ruminant. 
In  a  future  memoir,  on  the  Hyops  depressifrons,  a  suiline  animal, 
the  remains  of  which  were  found  in  the  same  locality,  will  be  de- 
tailed my  reasons  for  referring  to  the  genus  with  trenchant  canines 
the  fragment  of  calcaneum  and  metatarsal  bones  described  in  the 
preceding  pages. 


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